SPIO. 169 



accept Levinsen's 2 inclusion of the genus Nerine of Johnston under Spio. He is unaware 

 of any species coming within the description of the two species of 0. F. Miiller, 3 as given 

 by Fabricius, 3 since they have a pointed and rounded snout, two anal papillao, and branchiae 

 throughout the body. The first is 3 inches long and has sixty-eight to seventy-six seg- 

 ments ; the second 1 inch with forty-eight segments. He thinks the legendary plate of 

 De Blainville (19, ' Diet. Sc. nat.'), giving a figure of Spio seticornis, is probably a specimen 

 of Suriray's 2 or 3 lines long. Mesnil did much for this family in his able memoir in 

 Giard's < Bulletin. 5 



Cuvier (1817) linked on Spio as a member of his second Order, the Dorsibranchs, the 

 first division of which included the Nereids and Eunicids, with jaws, the second those 

 without them, like Spio and Arenicola, yet the Polynoids, with their horny jaws, are not 

 in agreement with this arrangement. 



Spio was included by Savigny (1820) amongst the Nereids, along with Polydora, and 

 in this association he was followed by De Blainville. 



Audouin and Milne Edwards (1834) placed the genus Spio under their Appendix 

 of forms Incertse sedis, the chief character being the very long, slender tentacles. They 

 considered that they were Nereids, perhaps approaching Syllis, since they had an unarmed 

 proboscis and uniramous feet deprived of branchiae. 



Grube made three species, viz. Spio filicomis (Miiller) Fabricius, Sp. seticornis (Miiller) 

 Fabricius, and S. crenaticomis, Montagu. 



Dalyell's 4 (1853) Nereis parva apparently belongs to this genus, though the species 

 is uncertain. 



De Quatrefages (1865) placed the genus Spio in the category of uncertain forms, and 

 following Polydora. He points out that the term Spio was used bj Konig for Terebella 

 cirrata, and adopted by Fabricius for two singular species, Spio seticornis and S. filicomis, 

 which he grouped with the Nereids, in his ' Fauna Grcenlandica.' The descriptions of 

 these, however, are so imperfect that their identification is uncertain. 



Claparede and Mecznikow 5 (1868) described an early larva of Spio Mecznilcowianus 

 in the telotroch condition, with two eyes, an oesophagus, largely distended body, and a 

 few tufts of cilia on the thickened ventral surface. A structure, which they term a 

 developing tentacle, lies behind the head. They also describe the segmental organs of 

 this species, which are normal in structure, and open behind the feet. Moreover, a 

 peculiar spermatophore is formed in the male, and finds exit by the segmental organs. 



Kuhlgatz 6 (1898) describes a new species of Spio (S. in versa), from the North Sea, 

 which so far as can be observed approaches Pygospio elegans. He gives an interesting 

 discussion as to the species of Spio described by former authors, and a table indicating the 

 distinctive characters of the several species. 



Giard 7 (1913) thought Montagu's Spio crenaticomis was the same as Aonis Wagneri, 



1 < Vid. Meddel. Nat. For./ 1883, pp. 92—380. 



2 < Zool. Danica Prod./ 1776, Nos. 2639 and 2640. 



3 f Fauna Greenland./ pp. 288 and 289. 



4 'Powers Creator/ vol. ii, p. 147, PI. XX, figs. 23—25. 



5 ' Zeitschr. f. wiss. Zool./ Bd. xix, p. 8 (sep. abdr.), Taf. xii, fig. 2c. 



6 ' Wissensch. Meersuntersuch./ Bd. iii, p, 151, Taf. ii, figs. 19 — 21. 



7 ( CEuvres Diverses/ p. 56. 



145 



